Electrochemical cells, or batteries, are commonly used as electrical energy sources. A battery contains a negative electrode, typically called the anode, and a positive electrode, typically called the cathode. The anode contains an electrochemically active anode material that can be oxidized. The cathode contains an electrochemically active cathode material that can be reduced. The electrochemically active anode material is capable of reducing the electrochemically active cathode material. A separator is disposed between the anode and the cathode. The battery components are disposed in a can, or housing, that is typically made from metal.
When a battery is used as an electrical energy source in an electronic device, electrical contact is made to the anode and the cathode, allowing electrons to flow through the device and permitting the respective oxidation and reduction reactions to occur to provide electrical power to the electronic device. An electrolyte is in contact with the anode, the cathode, and the separator. The electrolyte contains ions that flow through the separator between the anode and cathode to maintain charge balance throughout the battery during discharge.
There is a growing need to make batteries that are better suited to power contemporary electronic devices such as toys; remote controls; audio devices; flashlights; digital cameras and peripheral photography equipment; electronic games; toothbrushes; radios; and clocks. To meet this need, batteries may include higher loading of electrochemically active anode and/or cathode materials to provide increased capacity and service life. Batteries, however, also come in common sizes, such as the AA, AAA, AAAA, C, and D battery sizes, that have fixed external dimensions and constrained internal volumes. The ability to increase electrochemically active material loading alone to achieve better performing batteries is thus limited.
The electrochemically active cathode material of the battery is another design feature that may be adjusted in order to provide increased performance. For example, electrochemically active material that has higher volumetric and gravimetric capacity may result in a better performing battery. Similarly, electrochemically active material that has a higher oxidation state may also result in a better performing battery. The electrochemically active material that is selected, however, must provide an acceptable closed circuit voltage, or running voltage, range for the devices that the battery may power. The device may be damaged if the OCV or running voltages of the battery are too high. Conversely, the device may not function at all if the running voltage of the battery is too low. In addition, electrochemically active material, such as high oxidation state transition metal oxide, may be highly reactive. The highly reactive nature of such electrochemically active material may lead to gas evolution when the electrochemically active material is incorporated within a battery and is brought into contact with the electrolyte. Any gas that is evolved may lead to structural issues within the battery, such as continuity within the cathode, and/or leakage of electrolyte from the battery. The high oxidation state transition metal oxide may detrimentally react with other battery components, such as carbon additives, e.g., graphite; other additives, e.g., surfactant(s); and/or the separator. The high oxidation state transition metal oxide may also have a tendency to consume electrolyte, which may lead to other structural issues within the battery, such as cathode swelling, and unfavorable water balance within the battery. Also, a battery including high oxidation state transition metal oxide as an electrochemically active cathode material may, for example, exhibit instability and an elevated rate of self-discharge when the battery is stored for a period of time.
There exists a need to provide an electrochemically active cathode material for a battery that address the needs discussed above. The beta-delithiated layered nickel oxide electrochemically active cathode material of the present invention addresses, inter alia, these needs.